old_list = [[1, 2, 3], [4, 5, 6]]
new_list = []
for i in range(len(old_list[0])):
    #0-3    0.1.2
    little_list = []
    for j in range(len(old_list)):
        #0-2    0.1
        little_list.append(old_list[j][i])
    new_list.append(little_list)
print(new_list)